Researchers Unlock 96% Fidelity Chip-Scale Entangled Photons

The creation of efficient and scalable sources of entangled photons remains a crucial challenge for advancements in quantum technologies. Xu-Feng and colleagues at the University of Science and Technology of China, working with researchers at the University of Pannonia, now demonstrate a significant step forward with a compact, chip-based device capable of generating ultrabright entangled photons using electrical pumping. This innovative approach, which integrates a laser with a lithium niobate chip containing nanoscale waveguides, overcomes previous limitations in scalability and performance, achieving a high pair generation rate and exceptional entanglement fidelity. The resulting device promises to unlock new possibilities for secure communication, satellite-based quantum networks, and other applications reliant on robust and efficient entanglement.

Tunable Entangled Photons from Integrated Photonics

Entangled photon sources are fundamental to the development of quantum technologies. Creating sources that are both bright, efficient, and capable of generating a wide range of wavelengths remains a significant challenge, as existing sources often compromise between these key features, limiting their use in areas such as quantum communication, computation, and sensing. Integrated photonic circuits offer a promising solution, enabling precise control over photon properties and facilitating scalable manufacturing. This research focuses on developing a new integrated platform for generating high-performance entangled photon pairs with enhanced brightness, efficiency, and spectral tunability. The work investigates new materials and designs to improve photon collection efficiency, enhance entanglement fidelity, and broaden the range of wavelengths of generated photons, ultimately aiming to provide a practical and versatile entangled photon source for enabling future quantum technologies.

Integrated Chip for Entangled Photon Generation

This research details the fabrication and characterisation of an integrated lithium niobate chip designed to generate broadband, polarisation-entangled photon pairs. The chip incorporates a periodically poled lithium niobate waveguide for spontaneous parametric down-conversion and a polarisation rotator to manipulate the photons’ polarisation. Detailed measurements and comparisons with simulations validate the chip’s performance. Lithium niobate was chosen for its high nonlinear properties and transparency to light used in telecommunications. Measurements of a multi-mode interferometer within the chip showed low insertion loss, indicating minimal signal distortion.

Second harmonic generation measurements confirmed the uniformity of the waveguides and determined their phase-matching wavelengths, crucial for efficient entangled photon generation. The chip demonstrated a broad bandwidth for generating entangled photons, and measurements of the polarisation rotator confirmed its ability to manipulate the polarisation of the generated photons, essential for creating different entangled states. The chip provides a compact and integrated platform for generating and manipulating entangled photons, paving the way for practical quantum technologies.

Compact Hybrid Chip Generates Photon Pairs

Researchers have developed a compact and highly efficient source of entangled photons, overcoming previous limitations in scalability and performance. This new device integrates a laser with a thin-film lithium niobate chip, creating a system capable of generating a substantial number of entangled photon pairs, 4. 5 x 10 10 pairs per second for every milliwatt of power, and measuring just 15 x 20 millimeters. The key to this breakthrough lies in the hybrid integration approach, which combines laser technology and advanced materials science. By carefully engineering the lithium niobate chip, the team created waveguides and other optical components that efficiently generate and manipulate entangled photons.

The resulting source exhibits a broad bandwidth of 73 nanometers and maintains high fidelity, above 96%, across these wavelengths. This level of performance opens doors to several practical applications, including secure quantum communication and enhanced quantum sensors. Notably, the system’s low power requirements mean it could even be powered by a portable battery, greatly increasing its versatility and potential for real-world deployment. The researchers envision future developments focusing on further miniaturisation and integration, aiming to create fully functional quantum systems on a single chip.

High-Performance Entangled Photons from Hybrid Integration

This research demonstrates a compact, integrated source of entangled photons achieved through the hybrid integration of a distributed feedback laser with a thin-film lithium niobate chip. The resulting device generates high-quality entangled photon pairs with a peak generation rate of 4. 5 x 10 10 pairs per second per milliwatt, and a broad bandwidth of 73 nanometers. Importantly, the system achieves Bell-state fidelities exceeding 96% across multiple frequency channels without the need for low-temperature cooling, representing a significant step towards practical quantum technologies. The developed source offers substantial advantages for applications such as high-speed quantum key distribution via wavelength division multiplexing, satellite-based quantum communication, and entanglement-based quantum metrology. Future work will focus on fully integrating all necessary components onto a single lithium niobate platform, paving the way for more complex and versatile chip-scale quantum systems.